Power transmission mechanism



3 Sheets-Sheet l R. E. KELLER POWER TRANSMISSION MECHANISM June 17, 1952 Filed June "1, 1948 IN V EN TOR. 0.54: t. Maw;

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June 17, 1952 E KELLER 2,601,151

' POWER TRANSMISSION MECHANISM Filed June 7, 1948 3 Sheets-Sheet '2 INVENTOR. fizz 6 Kama BY I June 17, 1952 R. E. KELLER 2,601,151

POWER TRANSMISSION MECHANISM Filed June 7, 1948 3 Sheets-Sheet 5 w 64 m 51 60J -a5 73 =-L an I AUTO.-|5T STAGE D- a4-aa-so-m-csws-se-sa-al ao as-uo'(s4 FIXED T0 cns: nmu 60-85-506150 NEUTRAL PosmoN ILLUSTRATED Posmvs LOW D-85-8o-69-65-65-68-9I-88'O(|( men 1'0 case Tunu-sa-so) 52 E A [uae BY Patented June 17, 1952 UNITED STATES PATENT OFFICE POWER TRANSMISSION MECHANISM Rex E. Keller, Beverly Hills, Calif.

Application June 7, 1948, Serial No. 31,532

18 Claims.

This invention relates in general to power transmission mechanisms but particularly to and has for an object the provision of an automotive transmission mechanism of simple and economical design capable of ready application to and use on modern motor vehicles and particularly embodying a single planetary gear unit for use in connection with ordinary clutches, and particularly with single or double stage fluid coupling units and providing low, direct, overdrive, neutral, and reverse stages, and automatic low, direct, and overdrive and return.

Other and more detailed objects of my invention will appear as the description of my improved mechanism progresses.

I have shown a preferred type of mechanism embodying my improvements and certain modifications thereof in the annexed drawings, subject to further modification, within the scope of the appended claims, without departing from the spirit of the invention.

In said drawings:

Fig. 1 is a sectional view of a simple form of transmission mechanism in a plane cutting the main axis of the unit;

Fig. 2 is a transverse section of the same in a plane of Fig. 1, as viewed in the direction of arrows 2, 2;

Fig. 3 is a section in plane of Fig. 1, as seen in the direction of arrows 3, 3;

Fig. 4 is an enlarged fragmentary section in the plane of Fig. 1;

Fig. 5 is a table indicating elements of the unit of Figs. 1 and 4 differently connected to provide different gear ratios and speeds, the connected elements being indicated by reference characters in the table;

Fig. 6 is a section on a plane cutting the main axis and showing a modified form of transmission employing automatic and overdriving clutch or clutches and other features differing from the structure and arrangement of Fig. l;

Fig. '1 is a transverse section on line of Fig. 6;

Fig. 8 is a transverse section on line 88 of Fig. 6, showing details of a typical automatic clutch;

Fig. 9 is an enlarged partial section of the structure of Fig. 6;

Fig. 10 is a table of gear connections between the several elements of the form of transmission shown in Figs. 6 and 9; and

Fig. 11 is a partial section of a still different form of mechanism in the plane of its main axis using the sun gear anchored to the case instead 2 of the orbit gear for leverage purposes in underdrive and overdrive.

A characteristic common to all of the forms of transmission mechanism shown is the provision of but a single planetary gear unit, suitable means for shifting some of the elements relative to others and arrangement and means for operatively connecting all forms to an ordinary clutch or a fluid coupling unit, if desirable.

Initially, I will describe the form of mechanism shown in Figs. 1 to 4, inclusive, with reference also to Fig. 5, as follows: The unit is assembled in a case A formed of circular end walls and 3| and a cylindrical wall 32 held fixedly on the end walls by bolts 33 and nuts 34 so as to mount the complete unit concentrically relative to a driving shaft D and a driven shaft D. End walls 30 and 3| have internal teeth 30a and 3|a, respectively, and member 32 has internal orbit gear 32a. Inwardly of and immediately adjacent end walls 30 and 3| are similar pinion carrier discs 35 and 36 which are bored to receive opposite ends 31 and 38 of a plurality of shafts 39 on which planet gears 40, 40 ar mounted for rotation. A sun gear 4| is carried on driving shaft D and is adapted to mesh constantly with planet gears 40 while said planet gears also mesh with orbit gear 32a, thereby composing a complete planetary gear set. I

Driving shaft D is bored at 42 to telescopically receive a concentric reduced extension 43 of driven shaft D and is formed with external teeth 44, adapted to selectively engage internal teeth 45 and 46 formed on sun gear 4|. Carrier disc 36 has internal teeth 41 thereon and driven shaft D has external teeth 48 adapted to selectively mesh with teeth 41 or 3 la.

Carrier disc 35 has internal teeth 49 adapted at times to mesh with external teeth 50 on an extension 5| from the case C. Thus, when the unit is bodily shifted longitudinally of the driving-driven shaft axis the several elements are interconnected, in the manner shown in Fig. 5, and as hereinafter more fully explained, for establishing different gear ratios and correspondingly difierent speeds and direction of rotation of the driven shaft.

It will be observed, therefore, that when the unit is bodily shifted to the right as seen in Figs. 1 and 4, the driving teeth 44 of shaft D will engage the remote portion of internal teeth 45 of sun gear 4| while the teeth 48 of driven shaft D will engage with internal teeth 46 of sun gear 4|, thereby providing a direct driving connection between shafts D and D and permitting bodily rotation of the unit with said shafts. As shown in Figs. 1 and 4, the unit is shown in neutral position with teeth 46 unmesh d from teeth 45 and 46 of the sun gear.

A low gear connection between shafts D and D is obtained by shifting the unit A to the right to an extent only necessary to engage teeth 44 with teeth 45 and teeth 47 with teeth 43, simultaneously, thereby driving through sun gear 4i, pinions '40, orbit gear 32a and carrier36, orbit gear 32a being fixed to case C by meshing of teeth a and 50.

For providing a reverse gear drive the unit A is shifted to the left so that case C will be connected with carrier through elements 49 and 41; and gear teeth 3m with driven toothed-member 48,- and spur teeth 52 on sun gear 41 with case teeth 53. In such event, sun gear-4i is fixed to the case while the planet gears are rotated through carrier 36 and-power is applied to shaft D through orbit gear-32aand teeth am.

.Now, referring to Figs. 6, 7, 8, and 10 it will be observed that I have provided a somewhatdifferent form of mechanism from thatshown in Figs. 1 and 4, although similar results are accom plished in a slightly different manner. This optional form includes a housing H with end walls as and 6| held together by bolts 62, an outer circular wall-63'bearing an internal set of teeth 64 to form a ring or orbit gear, planet gears 65 carried onsspindles 66 and spacedly connecting carrier e .discs 61 and 63, a sun gear 69, a pair of centrifugal clutches 10-and H of a wellknown type, and a pair of overrunning clutches GI and SI all of which:elements are-adapted for selective interconnection when certain elements of the unit are bodily shifted, for providing different driving ratios with the drivenshaft. Shafts D and D are-partly telescopic as'in Fig. 1. Carrier disc 61 has internal gear teeth 43 adapted to engage case gear teeth on case Gas in Fig. 1,- and is recessed at 12 on its inner side to snugly receive the clutch unit 19. The wall of said recess has a plurality of grooves 13 which are adapted at .times to receive clutch portions 74 diametrically extended-from bodies 75 and which are normally urged inwardly into non-clutching positions by springs 16 but are thrust, outwardly toward clutching positions by accelerating the speed of the clutch bodies i5 (Fig. 8). This type of clutch is-well known and two forms thereof are illus trated in patents No. 2,286,549'and No. 2,182,385, but any other type of automatic clutch may be here used.

The inner driving member. T! of the clutch has a hub 18 embracing driving shaft D and a web 73 operatively supports members 75. Web F9 has a hub 80 extended concentrically into and freewheelingly connected with sun gear.69 through rollers-BI operating .in inclined peripheral recesses 82 of usualcharacter, thereby permitting differential rotation of carriert'l', clutch member 11, and sun gear-69.

. Clutch member H has internal teeth83 adaptedattimestoengage teeth 84011 shaftD. Shaft ,D also has teeth 85 spaced to the right as seen 4 in Fig. 5, from teeth 83, whereas the coaxial driven shaft D has teeth 86, 81, and 88 formed spaced apart thereon. The web of sun gear 69 has internal teeth 90; clutch member 19' at its hub 80 has teeth 89; carrier 68 has internal gear teeth 9|; and end wall 6! has internal teeth 92, and end wall has internal teeth 93 thereon, by means of which said sun, planet, and orbit gears, the elements of the transmission may be selectively interconnected for aifording different gear ratios to vary the torque applied toand direction of rotation of the driven shaft D. Free wheeling rollers Bl similar to those shown at 8| are employed between clutch II and carrier disc 68 and are such as are shown in Fig. 7.

Asindicated in the table of Fig. 10, this type of transmission provides three stages of automatic operation plus neutral, positive reverse,

positive high, and positive low stages. The elements shown in Figs. 6 and 9 are relatively in neutral positions.

Referringto Fig. 9, it will be noted that: carrier GT-serves as a drum for clutch ii! while sungear ESserves as a drum for clutch H, said carrier .67 and sun gearhaving rims .67 and 69, respectively, with recesses 13 (Fig. 8) therein for receiving the clutch elements 14.

Automatic first stage is effected by shifting unit H to the right as seen in Fig. 9, thereby meshing driving teeth 84 with clutch teeth..83, and imparting forward motion through member 80 and free wheeling clutch 8| to sun gear 69, thence through pinions and shaft 66 to carrier discsv 67 and 63, thence through free wheeling clutch 8| to member 8% of clutch H and through teeth 39 and teeth 87 to shaft D, the member E0 being fixed to case C by engagement of teeth 50 and 93.

A second automatic stage is obtained by this same-shift with teeth 84 -andteeth-83 and-teeth E9 and teeth 81 engaged, but through the driving of member 36 of automatic clutch which becomes automatically operative above certain speeds, the carrierB! is rendered directly operative and the driving connection with shaft B being maintained through shaft 66, carrier 68, free wheeling clutch 8|, member-86 ofclutchJl and teeth 89 and teeth 87. In this stage clutch 8| free wheels.

A third automatic stage is obtained while the driving connection remains through teeth 84-83, automatic clutch unit 70, through member .80, carrier 61, shaft 66, pinions .65, sun gear 69, thence through automatic clutch ll, member and teeth 89-81, to shaft D. In this instance both clutches 3| and 8| free wheel, but the overdrive connection is positive.

Reverse gear connections are established by shifting unit H to the left and engaging internal teeth 96 with driving teeth84 and teeth 49, 50 and teeth 92 with driven teeth 88. Thus, the sun gear rotates forwardly while the carriers 61 and 68 are fixed to case C and orbit gear-64 and housing H rotates reversely for imparting reverse rotation to driven shaft D through teeth 92 and 83.

A positive high gear connection is effected by shifting unit H to the right until sun gear 69, through its internal teeth 99 engages -both sets of teeth and85 which are carried cnshafts D and D, respectively.

A positive low gear driving connection is obtained by shifting H to the right to an extent which will engage teeth .99 with teeth 85, and teeth 93 with teeth 50 of the case, and teeth-9| with teeth 88; thereby imparting motion to driven shaft D through sun gear 69, shaft 66, and carrier 68 to shaft D.

For shifting unit A of Figs. 1 and 4 and unit H of Figs. 6 and 9, bodily, a shift collar 3| or 6| as the case may be, is provided at an end of the housing for receiving a conventional shifting yoke.

Fig. 11 illustrates a. third form of mechanism embodying similar elements but arranged differently than corresponding elements of the previously described forms, although the sun gear instead of the orbit gear is connected to the case, and effects similar operation. In this instance, a suitable housing H is provided with end walls I and IOI joined by a circular wall I02, end IOI being shown with a shift collar I03 adapted to receive a shifting member I04.

In said housing is mounted an orbit gear I05, sun gear I00, pinions I01 on shafts I08 connected with a member I00, a pair of automatic clutches H0 and III including drums H2 and H3, respectively, and free wheeling clutches II4 nad I I5, respectively, which are provided between clutch member I I2 and orbit gear I05 and clutch member H3 and wall IOI of housin H.

Wall I00 has teeth H6 adapted at times to engage teeth 50 on extension 5I of case C and bears ends of pinion shafts I08 so that together with member I09 the pinions are operatively separated for connecting sun gear I06 with orbit gear I05. Hence, the housing H, pinions I01, and member I09 rotate planet-like and together around sun gear I06 while orbit gear I05 in this case is independent of the housing. Shaft D carries a member II1 formed with spaced sets of teeth H8 and H0 while driven shaft D has a member I thereon formed with a single set of teeth I2I.

Sun gear I05 has internal teeth I22 clutch member II2 has internal teeth I23, a member I24 is fixed to orbit gear I05 and has internal teeth I25, and member II3 has internal teeth I26 thereon for selective engagement with said teeth on the driving and driven shafts D and D. Members I09 and I24 constitute the supporting members for the clutch elements of the automatic clutches H0 and III (similar to Fig. 8), while members H2 and H3 constitute the outer or driven members of said clutches.

In the mechanism of Fig.- 11, the sun gear I00 is adapted to be connected with case C through teeth I22-50 and thus held against rotation and orbit gear I05 overruns driven element (drum) II2 of clutch H0, and the driving element of clutch IIO always rotates with housing H and pinions I01. The driving element I24 and driven element II3 are selectively engageable with driven shaft D" through teeth I25 or I26 and teeth I2 I, while housing H and element I09 free-wheel on element II3. Thus, the unit H rotates at a speed less than high ratio and drives shaft D through clutches H0 and III.

Shifting of unit H is made bodily by means of member I04 with the enclosed elements-to the left for forward automatic shifting and overdriving, and to the right for reverse driving of shaft D. When in automatic low, direct and overdrive arrangement the drive is through teeth II9, I23, members H2, H4, I05, pinions I01, members I00, IOI, II5, teeth I26, I2I, members I20, D. Direct and overdriving characteristics are provided by clutches H0 and III moving independently of each other, or together.

In reverse gear, unit H having been shifted to the right the planetary carrier is held against rotation through teeth H6 and teeth while sun gear I06 is driven through teeth II8-I22. Orbit gear I05 imparts reverse motion to B through I24, teeth I25, I2I, and member I20.

Of course, it will be understood that while I have herein shown and described the unit A and its included elements as commonly shiftable relative to elements on shafts D and D said shafts or the elements thereon may as well be shiftable relative to said unit for changing operating conditions of the mechanism, or connections could be made by employment of ordinary shift collars.

I claim:

1. A power transmission mechanism comprising: coaxial driving and driven shafts, a stationary case and a, gear changing unit including a housing, a single planetary gear set within the housing embodying sun, planet, and orbit gears, and a planet gear carrier, and means associated with said planetary set and said shafts and arranged for selective interconnection in response to the relative shifting of the planetary elements and the elements on said shafts and on said case,

' for varying the torque applied to the driven shaft, and a centrifugal clutch operatively connecting the sun gear and carrier of the planetary gear set upon the attainment of synchronization between the driving and driven elements of said clutch.

2. A power transmission mechanism comprising: coaxial driving and driven shafts, a stationary case and a gear changing unit including a housing, a single planetary gear set Within the housing embodying sun, planet, and orbit gears, and a planet gear carrier, means associated with said case, carrier, sun, and orbit gears and said shafts arranged for selective interconnection in response to the relative shifting of the planetary elements and the elements on said shafts and on said case, for varying the torque applied to the driven shaft, a centrifugal clutch operatively connecting the sun gear and carrier of the planetary gear set upon the attainment of synchronization between the driving and driven elements of said clutch, and an overrunnin clutch operatively connecting one of the elements of the centrifugal clutch and one of the driving gears of the planetary set.

3. A power transmission mechanism comprising: coaxial driving and driven shafts, a stationary case and a gear changing unit including a housing, a single planetary gear set within the housing embodying sun, planet, and orbit gears, and a planet gear carrier, and means associated with said case, carrier, sun, and orbit gears and said shafts arranged for selective interconnection in response to the relative shifting of the planetary elements and the elements on said shafts and on said case, for varying the torque applied to the driven shaft, and a centrifugal clutch embodying driving and driven elements adapted at times to be locked together, a free wheeling clutch connecting said driven element with the planet gear carrier of the planetary set and therethrough to the driven shaft and means for positively connecting the driving element of the free wheeling clutch with the driving shaft.

4. A power transmission mechanism comprising: coaxial driving and driven shafts, a stationary case, and a gear changing unit including a housing, a single planetary gear set within the housing embodying sun, planet, and orbit gears, and a planet gear carrier, and means associated with said case, carrier, sun, and orbit ing: coaxial driving and driven shafts, a stationary case into which the driving shaft extends for operative connection with a motor, a variable speed unit including a housing and a planetary gear set enclosed by said housing and including a sun gear, an orbit gear fixed to said housing, a planet gear carrier and planet gears borne by said carrier and permanently connecting the sun gear with the orbit gear, said case having a circumferentially toothed extension embracing the drive shaft and arranged for selective connection at times with said housing, said carrier and said sun gear, clutch teeth on said driven shaft arranged for selective connection with clutch teeth on said carrier and on said housing, said housing and the gears enclosed thereby being shiftable bodily together axially of said shafts, for driving the driven shaft at differentspeeds as influenced by the shifted position of the unit.

6. A power transmission mechanism as set forth in claim 5 in which: the shifting of said unit in one direction will lock the housing of the unit to the case against rotation and operatively connect the planetary set through the sun gear and the carrier with the driven shaft and provide a direct driving connection between said shafts.

7,. A power transmission mechanism as set forth in claim 5 in which: the shifting of said unit in one direction will lock the housing of the unit to the case against rotation and operatively connect the planetary set through the sun gear and the carrier with the driven shaft and provide a direct driving connection between said shafts, and when said unit is reversely shifted will lock. said carrier against rotation and rotate the orbit gear and housing and operatively connect said shafts to provide speeds of less than one to one ratio.

8. A power transmission mechanism comprisingpcoaxial driving and driven shafts, a stationary case into which the driving shaft extends for operative connection with a motor, a variable speed unit including a housing and a planetary gear set enclosed by said housing and including a sun gear, an orbit gear fixed to said housing, a planet gear carrier and planet gears borne by said carrier and permanently connecting the sun gear with the orbit gear, said case having a circumferentially toothed extension embracing the drive shaft and arranged for selective connection at times with said housing, said carrier and said sun gear, clutch teeth on said driven shaft arranged for selective connection with clutch teeth on said carrier and on said housing, said housing and the gears enclosed thereby being shiftable bodily together axially of said shafts, for driving the driven shaft at different speeds as influenced by the shifted position of the unit, said carrier including spaced but cross-connected members with the planet gears therebetween, a centrifugal clutch including a driving member drivingly engageable with the driving shaftand a driven member rotatable with the carrier whereby when the driving and driven members of the centrifugal clutch are in synchronism said driving member and said carrier will be locked for rotation together.

9. A power transmission mechanism comprising: coaxial driving and driven shafts, a stationary case into which the driving shaft extends for operative connection with a motor, a variable speed unit including a housing and a planetary gear set enclosed by said housing and including a sun gear, an orbit gear fixed to said housing, a planet gear carrier and planet gears borne by said carrier and permanently connecting the sun gear with the orbit gear, said case having a circumferentially toothed extension embracing the drive shaft and arranged for selective connection at times with said housing, said carrier and said sun gear, clutch teeth on said driven shaft arranged for selective connection with clutch teeth on said carrier and on said housing, said housing and the gears enclosed thereby being shiftable bodily together axially of said shafts, for driving the driven shaft at difierent speeds as influenced by the shifted position of the unit, said carrier including spaced but cross-connected members with the planet gears therebetween, a centrifugal clutch including a driving member drivingly engageable with the driving shaft and a driven member rotatable with the carrier whereby when the driving and driven members of the centrifugal clutch are in synchronism said driving member and said carrier will be locked for rotation together, and a free wheeling clutch between the driving member of the centrifugal clutch and said sun gear, so that at times the driven shaft may over run the driving shaft through the connection of the carrier with the driven shaft and the connection of the driving member of said centrifugal clutch with the driving shaft.

10. A power transmission mechanism comprising: coaxial driving and driven shafts, a stationary case into which the driving shaft extends for operative connection with a motor, a variable speed unit including a housing and a planetary gear set enclosed by said housing and including a sun gear, an orbit gear fixed to said housing, a planet gear carrier and planet gears borne by said carrier and permanently connecting the sun gear with the orbit gear, said case having a circumferentially toothed extension embracing the drive shaft and arranged for selective connection at times with said housing, said carrier and said sun gear, clutch teeth on said driven shaft arranged for selective connection with clutch teeth on said carrier and on said housing, said housing and the gear enclosed thereby being shiftable bodily together axially of said shafts, for driving the driven shaft at different speeds as influenced by the shifted position of the unit, said carrier including spaced and cross connected members embracing the driving and driven shafts respectively, cooperating means on one of said carrier members and on said case for locking the carrier to said case against rotation while the sun gear is locked to the driving shaft and the gear housing is locked to the driven shaft.

11. A power transmission as set forth in claim 5 in which said carrier includes a pair of axially spaced members connected for common rotation, on opposite sides of the sun gear, means for selectively locking one of the carrier members and the housing to said case when the unit is shifted in one direction, means for locking the housing to the driven shaft when said unit is shifted so as to lock the carrier to the case and means for simultaneously therewith locking the sun gear to the driven shaft, and a centrifugal clutch associated with each carrier member and including a driving member and a driven member, the driving member of one clutch arranged for driving connection with the driving shaft and free wheeling connection with the sun gear and driving connection with the associated driven member of the clutch when the clutch members are in synchronism, the driving member of the other clutch arranged for driving connection with the driven shaft and for free wheeling connection with the associated carrier member, the driven member of the second clutch being permanently connected with the sun gear.

12. In a power transmission mechanism, in combination with a motor having a stationary case anda driving shaft extended therefrom: a transmission unit bodily shiftable axially of the drive shaft and including a housing, a planetary gear set, a pair of centrifugal clutches each having a driving element arranged to be drivingly connected with the driving shaft and a driven element arranged for connection through said planetary gear set with the driven shaft, a free wheeling clutch drivingly connecting the driving element of each centrifugal clutch with the driving shaft, said planetary gear set including an orbit gear rotatable with said housing, a sun gear, a planet gear carrier including a pair of discs connected for corotation, and planet gears supported on said carrier for operatively connecting said sun and orbit gears, and a driven shaft coaxial with said drive shaft, said motor case having an externally toothed cylindrical extension telescoping said drive shaft, one disc of said carrier and an adjacent end wall of said housing having internal teeth arranged for selective engagement with the teeth on said extension when said transmission unit is axially shifted in opposite directions, said driven shaft having external teeth and a second end wall of said housing having internal teeth adapted to mesh only when said unit is shifted for engaging a carrier disc with said case extension, said driving and driven shafts having other sets of external clutch teeth and said sun gear, carrier and the driving members of said centrifugal clutches having sets of internal clutch teeth arranged for selective interconnection in response to the shifting of said unit for varying the torque applied to the driven shaft.

13. In a power transmission mechanism as set forth in claim 12, in which one of said carrier discs is operatively associated with and arranged to be driven by the driving member of one of said centrifugal clutches and said sun gear is drivingly connected with the driving member of the other centrifugal clutch.

14. In a power transmission mechanism, in combination with a motor having a stationary case and a driving shaft extended therefrom: a transmission unit bodily shiftable axially of the drive shaft and including a housing, a planetary gear set, a pair of centrifugal clutches each having a driving element arranged to be drivingly connected with the driving shaft and a driven element arranged for connection through said planetary gear set with the driven shaft, a free wheeling clutch drivingly connecting the driving element of each centrifugal clutch with the driving shaft, said planetary gear set including an orbit gear rotatable with said housing, a sun gear, a planet gear carrier including a pair of discs connected for corotation, and planet gears supported on said carrier for operatively connecting said sun and orbit gears, and a driven shaft coaxial with said drive shaft, said motor case having an externally toothed cylindrical extension telescoping said drive shaft, one disc of said carrier and an adjacent end wall of said housing having internal teeth arranged for selective engagement with the teeth on said extension when said transmission unit is axially shifted in opposite directions, said driven shaft having external teeth and a second end wall of said housing having internal teeth adapted to mesh only when said unit is shifted for engaging a carrier disc with said case extension, said driving and driven shafts having other sets of external clutch teeth and said sun gear, carrier and the driving members of said centrifugal clutches having sets of internal clutch teeth arranged for selective interconnection in response to the shifting of said unit for varying the torque applied to the driven shaft, the driving members of said centrifugal clutches being respectively arranged to free wheelingly drive said sun gear and a second carrier disc.

15. In a power transmission mechanism, in combination with a motor having a stationary case and a driving shaft extended therefrom: a transmission unit bodily shiftable axially of the drive shaft and including a housing, a planetary gear set, a pair of centrifugal clutches each having a driving element arranged to be drivingly connected with the driving shaft and a driven element arranged for connection through said planetary gear set with the driven shaft, a free wheeling clutch drivingly connecting the driving element of each centrifugal clutch with the driving shaft, said planetary gear set including an orbit gear rotatable with said housing, a sun gear, a planet gear carrier including a pair of discs connected for corotation, and planet gears supported on said carrier for operatively connecting said sun and orbit gears, and a driven shaft coaxial with said drive shaft, said motor case having an externally toothed cylindrical extension telescoping said drive shaft, one disc of said carrier and an adjacent end wall of said housing having internal teeth arranged for selective engagement with the teeth on said extension when said transmission unit is axially shifted in opposite directions, said driven shaft having external teeth and a second end wall of said housing having internal teeth adapted to mesh only when said unit is shifted for engaging a carrier disc with said case extension, said driving and driven shafts having other sets of external clutch teeth and said sun gear, carrier and the driving members of said centrifugal clutches having sets of internal clutch teeth arranged for selective interconnection in response to the shifting of said unit for varying the torque applied to the driven shaft, the driving members of said centrifugal clutches being respectively arranged to free wheelingly drive said sun gear and a second carrier disc, the driving members of said centrifugal clutches being respectively driven by the driving shaft and serving to drive the driven shaft when said unit is appropriately shifted.

16. In a power transmission mechanism as set forth in claim 12, in which one of said carrier discs is operatively associated with and arranged to be driven by the driving member of one of said centrifugal clutches and said sun gear is 1 1 drivingly connected with the driving member of the other centrifugal clutch, and means for shifting said unit to differentially apply torque to the driven shaft and for reversing the direction of rotation thereof.

17. In a power transmission mechanism as set forth in claim 12, in which one of said carrier discs is operatively associated with and arranged to be driven by the driving member of one of said centrifugal clutches and said sun gear is drivingly connected with the driving member of the other centrifugal clutch, and means for shifting said unit to differentially apply torque to the driven shaft and for reversing the direction of rotation thereof, the connections between said drive shaft, said sun gear and the driving member of 'one of said centrifugal clutches being such that the sun gear will be positively driven, when the unit is shifted in one direction, and when shifted in an opposite direction the sun gear will be free 12 drivingly connected with the driving member of the other centrifugal clutch, the connections between said shafts and said centrifugal clutches being such that when the driving members of said clutches are connected respectively with the driving and driven shafts by the shifting of the unit in one direction power will be applied to the driven shaft through the first clutch when the sun gear and finally through the second clutch.

REX E. KELLER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,159,426 Dunn May 23, 1939 2,182,385 Neracher Dec. 5, 1939 2,218,813 Cotterman Oct. 22, 1940 2,248,492 Cotterman July 8, 1941 2,257,333 Cotterman Sept. 39, 1941 2,311,209 Carnagua Feb. 16, 1943 FOREIGN PATENTS Number Country Date 5,835 Great Britain Mar. 11, 1907 

